1. Field of the Invention
The present invention relates to a polypropylene resin composition and to an injection molded article obtained by use of the resin composition. In particular, the present invention relates to a polypropylene resin composition excellent in rigidity and impact strength, particularly in impact strength at low temperature, and to an injection molded article obtained by use of the resin composition.
2. Description of the Related Art
Polypropylene resins are widely employed for molded articles, etc. due to their excellent mechanical properties and processabilities. In particular, they are used in automotive materials that are required to have excellent impact strength, rigidity and thermal properties such as thermal distortion temperature.
Heretofore known are blending an ethylene-xcex1-olefin random copolymer or a vinyl aromatic compound to a polypropylene resin in order to improve the impact strength of polypropylene resins, and blending a filler such as talc to a polypropylene resin in order to improve the impact strength or thermal properties such as thermal distortion temperature.
For example, Japanese Patent Laid-Open No. 6-192500 discloses a propylene-based resin composition comprising a propylene-based polymer and an ethylene-xcex1-olefin copolymer with a flexural modulus of 2000 kg/cm2 or less, the resin composition having an improved impact resistance at normal temperature and an improved impact resistance at low temperature and having a well-balanced physical properties including rigidity and impact resistance. Further, it also discloses that fillers such as talc, and polystyrene resin and styrene-butadiene rubber can be blended.
In addition, Japanese Patent Laid-Open No. 8-302108 discloses a thermoplastic resin composition containing a crystalline polypropylene, an ethylene-butene-1 copolymer rubber, an ethylene-propylene copolymer rubber and talc, the resin composition being excellent in rigidity and impact resistance and requiring a short molding cycle as an injection molding processability.
However, the propylene-based resin composition and thermoplastic resin composition described in the above-cited publications of patent applications are still insufficient in rigidity and impact strength, particularly, in impact strength at low temperature and, therefore, further improvement is desired.
The object of the present invention is to provide a polypropylene resin composition excellent in rigidity and impact strength, particularly in impact strength at low temperature, and to provide an injection molded article obtained by use of the resin composition.
The present invention provides a polypropylene resin composition comprising (A) from 40 to 98% by weight of polypropylene resin, (B) from 1 to 30% by weight of basic magnesium sulfate fiber having a surface treated with montan wax wherein fibers contained in primary fibers have an average fiber length of from 7 to 10 xcexcm and the percentage of primary fibers containing fibers having a fiber length of 20 xcexcm or more is 10% by weight or less and (C) from 1 to 30% by weight of talc, provided that the total weight of the components (A), (B) and (C) is adjusted to 100% by weight. The present invention also provides an injection molded article obtained by use of the foregoing resin composition.